We are testing the hypothesis that Streptococcus mutans is responsible for a measurable amount of decay in humans. Rampant caries individuals, i.e. individuals with greater than or equal to 10 carious teeth, have high levels of Strep mutans in their plaque. We are making a bacteriological diagnosis of Strep mutans infection and treating these individuals topically with either 5% Kanamycin or 1.23% NaF in a pleasant tasting gel. The subjects are treated twice a day for a one week period on two occasions, i.e. prior to the placement of dental restorations and immediately after the placement of the restorations. Fissure, and proximal plaque samples and saliva are cultured before and after each treatment period and at the recall periods for total viable counts, Strep mutans and Strep sanguis counts. A placebo group is included. Subjects are randomly assigned to the treatment groups. The clinical scoring of caries and the bacteriological analysis are performed in a double blind procedure. An I.N.D. for chlorhexidine gluconate has been filed with the F.D.A., and if approved chlorhexidine will be used in these studies. In separate studies we are exploring the combined usage of chemotherapy and mechanical debridement in the treatment of gingivitis and periodontitis. Institutionalized subjects who present severe gingivitis will be treated with Nystatin, penicillin and scaling.